Nobody Is Withholding Your Tax Any More
An employer withholds tax from every paycheque, which is why most people spend their working lives never thinking about when tax is due, only how much. Retirement removes that machinery. Social Security withholds nothing unless asked, IRA custodians withhold only what you elect, and brokerage income has nothing withheld at all. The tax system still expects payment through the year, and the penalty for missing that is charged by the quarter.
- The answer:: Pay through the year, either by electing withholding on your income sources or by making quarterly estimated payments on Form 1040-ES.
- The safe harbour:: Pay at least 100% of the prior year's total tax, or 110% if your income was above the threshold, and no underpayment penalty applies regardless of what this year's liability turns out to be.
- The other one:: Paying 90% of the current year's actual tax also works, but requires forecasting a year you are still living in — which is why the prior-year test is the one most people use.
- Withholding beats estimates on timing:: Estimated payments are credited when made, so a late one leaves earlier quarters short. Withholding is treated as paid evenly across the year even if it all happens in December.
Where the AI summary above gets this wrong
"If you owe less than $1,000 when you file, you do not need to worry about estimated taxes."
That's surface-true. Here's what it misses:
- The penalty is charged quarter by quarter — It is not decided by the balance on your return in April. Each quarter is tested separately, so you can be owed a refund overall and still be penalised for a quarter that was underpaid — which is what happens when a large withdrawal in March is covered by a payment in December.
- The safe harbour is the point, not the balance due — Framing it around what you owe at filing misses the mechanism that actually protects you. Paying 100% or 110% of last year's tax removes the penalty even if this year's liability turns out to be far larger — which is exactly what a Roth conversion year looks like.
- Withholding and estimates are not interchangeable — They are treated differently in time. Withholding is deemed paid evenly through the year whenever it actually occurred, which makes a December withholding election a repair tool that an equally large December estimated payment cannot match.
01 Where the withholding went
Every source of retirement income has its own default, and most default to nothing. Social Security withholds only if you file a request. An IRA or 401(k) distribution withholds according to what you elect, and it is possible to elect zero. Dividends, interest and realised gains in a brokerage account have nothing withheld at all.
Meanwhile the obligation has not changed. Federal income tax is a pay-as-you-go system: the liability is expected to be paid roughly as the income arises, not settled in a lump the following April.
The gap between those two facts is where the underpayment penalty lives. It catches people in their first retired year almost as a rule, because thirty years of employment taught them that tax timing is somebody else's job.
02 The safe harbours, and why the prior-year one wins
Two tests avoid the penalty. Pay at least 90% of the tax you actually owe this year, or pay at least 100% of last year's total tax — 110% if your prior-year income was above the threshold. Meeting either is enough.
The prior-year test is the useful one, because last year's tax is a number you already have. The current-year test requires forecasting income you have not finished earning, and it fails precisely when income is unpredictable — which is when the penalty would otherwise bite.
It is at its most valuable in a year with a large one-off event. Someone doing a substantial Roth conversion may multiply their tax several times over, and the prior-year harbour still holds: pay the percentage of last year's much smaller bill, and the penalty does not apply even though a large balance is due in April.
Shows: how much more must be withheld or paid in estimates this year to land inside the prior-year safe harbour, whatever this year's income turns out to be. Ignores: the current-year alternative safe harbour, state estimated tax, and the timing rule that treats estimates quarter by quarter.
Source: Topic no. 306, Penalty for underpayment of estimated tax
03 Quarters, and the December repair
Estimated payments are due four times a year, and the periods are not even quarters — the deadlines fall in April, June, September and the following January. Each period is tested on its own, so paying the right annual total in the wrong pattern still produces a penalty for the periods that were short.
This is where withholding has an advantage that is easy to miss. Tax withheld is treated as paid evenly across the year no matter when it was actually withheld. An IRA distribution taken in December with a large amount withheld is therefore credited as though it had been spread from January, which can retroactively cure earlier quarters that estimated payments cannot.
The practical arrangement for many retirees is to skip estimates entirely: take the year's required distribution late, elect withholding on it large enough to cover the whole liability, and let the even-payment treatment handle the timing. One transaction, no quarterly diary.
The first retired tax year is the one that catches people, and the reason is habit rather than ignorance. You spend decades where tax timing is handled invisibly, then the machinery stops and nothing announces it. The fix I have seen work best is boring: take the required distribution in November or December, elect withholding on it big enough to cover the whole year, and never think about quarterly dates again. It works because withholding is treated as spread across the year — one of the few places where the rules are more forgiving than they look.
FAQ
Do I have to make estimated tax payments in retirement?
You have to pay through the year one way or another. That can be quarterly estimated payments, or withholding elected on Social Security, pension or retirement account distributions. What is not available is waiting until April with nothing paid in.
What is the safe harbour for estimated taxes?
Paying at least 100% of the prior year's total tax avoids the underpayment penalty regardless of this year's liability, rising to 110% if your prior-year income was above the threshold. Paying 90% of the current year's actual tax also qualifies.
Is withholding better than estimated payments?
For timing, yes. Withholding is treated as paid evenly across the year whenever it actually occurred, while an estimated payment counts only from when it is made. That makes a December withholding election able to repair earlier underpaid quarters in a way a December estimate cannot.
Sources
Regulator references
- Publication 505, Tax Withholding and Estimated Tax · Internal Revenue Service · 2025The pay-as-you-go rules, the safe harbours, and how withholding differs from estimates.Last verified: 2026-09-07
- Topic no. 306, Penalty for underpayment of estimated tax · Internal Revenue Service · 2025When the penalty applies and how it is computed quarter by quarter.Last verified: 2026-09-07
- About Form 1040-ES, Estimated Tax for Individuals · Internal Revenue Service · 2025The quarterly payment mechanism and its due dates.Last verified: 2026-09-07
Calculator unit tests · the assertions this page's worked example is checked against, and their last result
Changelog
- 2026-09-07 — initial publish (new format)
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Jordan Reeves
Founder of Talk Through Wealth. A software engineer for over a decade before turning to retirement planning, Jordan built the projection engine after watching family members get fragmented, country-by-country advice that never reconciled. He writes about retirement the way the engine computes it: month-by-month, lifetime-long, and skeptical of any rule of thumb that hasn't been run through the math.